In the last two days the Bay of Plenty has been shaken by hundreds of earthquakes, some greater than magnitude 4, and most of them relatively shallow (less than 15km) . This means shaking at the surface has been significant, but we have not read of any people getting hurt, thankfully. Our whānau at Te Kura O Te Pārao are less than 20km from the middle of this swarm, and the evidence on their station is clear:
The region has been at the mercy of Tāwhirimātea *and* Rūaumoko in recent months an our thoughts are with those enduring the shaking while recovering from the recent storms.
This particular swarm appears to happen very near the natural geothermal area of Awakeri, which is part of the surface expressions of the Taupō Volcanic zone (TVZ). Below is an image from the geothermal website of nz that shows the geothermal areas of the TVZ, including Awakeri:
The COVID-19 pandemic is paralyzing our ways of life, as we are hunkered down in a Level 4 lock-down. Businesses are closed, and work is moved to home, where possible. Schools are closed, and we live in our “bubbles.” Many of the seismic stations in the Ru network of school seismometers continue to operate, however, and we wanted to share with you some interesting observations. Here is a figure from our station at St. Mary’s Catholic Primary School in Rotorua:
The horizontal scale starts on January 1st of this year, and ends today, April 9th. The vertical scale is the average noise level at the station. There is a lot to see in here. First, the smallest consistent variations are between the days and the nights; Rotorua and St. Mary’s Primary School are much quieter during the nights than during the days. The next scale up, you can see that every 7 days, there is a period of low noise. These are the weekends, which are generally quieter than the weekdays. At an even larger time scale, we see that St. Mary’s station was less noisy during the Summer Holiday than during term 1 of school. Until two weeks ago, when school closed again, and noise levels dropped to its lowest levels.
This shows that seismometers are sensitive to the noise we humans make, even the not fully grown ones. In this case, the exceptionally low noise levels during the lock-down, lower than the Summer Holiday levels, indicate that station SMC2 is (normally) sensitive to human noise beyond the classroom, such as cars driving in the street. If you don’t believe us, please read the GEONET news, where it is reported that the lock-down in Auckland can be sensed all the way in a borehole 300 m under ground!
Yesterday, an eruption on Whakaari led to injuries and loss of lives. Our thoughts are with the whanau of those affected by this tragic event. We have been getting a lot of inquiries about this eruption, so we decided to write up what we know about the seismology associated with this eruption.
Whakaari is a volcano that is part of the Taupo Volcanic Zone, and forms a small island in the Bay of Plenty.
As far as we can tell, none of the Ru stations recorded the signals associated with the eruption, but GEONET operates seismic stations on the island:
The seismic data for station WIZ are plotted below. We annotated the time of the eruption. You can see that in the day(s) leading up to this, there were some small spikes in the data indicative of small local earthquakes. In addition, we can see a few hours of low-amplitude “rumbling” of Whakaari on the 8th of December:
Seismic station WSRZ is closer to the top rim of the volcano, and recorded this:
It looks like the amplitudes of the seismic signals were elevated on the 7th and 8th of December, but things actually calmed down on the 8th before the eruption… After the eruption, small impulsive signals may be from brittle failure of the rocks (small earthquakes).
It is difficult — if not impossible — to predict volcanic eruptions, and even after the fact it is hard for us to say whether signals prior to the eruption were out of the ordinary for Whakaari. The experts at GNS have had a elevated warning in place for Whakaari since October, based on seismic signals such as these, and gas sensing. In addition, an M5.9 earthquake at 115 km depth occurred on November 24th with its epicentre about 10km from Whakaari. As with all geological tragedies such as these, we hope we can learn more about the rumblings of Rūaumoku, reducing risk in future calamities.
A recent swarm of earthquakes in Northland prompted an article in the New Zealand Herald that features our Whangarei Girls High School station WGHS1, and station manager Nick Major. What a great article, and congratulations to Nick and the girls in Whangarei to keep an ear out for earthquakes up North!
In recent months we have added many new schools to our network, including Maungatapu Primary School. Under direction of Chris Dixon, this school is very active in the sciences. Through the Ru network, it is able to also connect its Maori language immersion programme, for example; have a look at their “Ru Whenua” posters!
All their hard work has attracted the attention of local media, resulting in this great article about their recordings of a local swarm of earthquakes. Well done, Edward, Jackson, Jamie, and all the others at Maungatapu School!
Shortly after midnight, last night, a severe earthquake struck the South Island. The full extent of the damage is not clear yet, and of course the members of the Ru network think about those affected by this event.
The seismic networks computed the thrust motion on the fault in a matter of minutes, and in this case the motion on the fault warranted a tsunami warning.
The New Zealand Herald features an article with the first reactions from geonet scientists. The mention of the Hope Fault is interesting. This fault is the southern-most fault of the Marlborough Faults (as far as we know!), which extend from the Alpine Fault. However, both Geonet and the USGS indicate a more southern placement of the epicentre. Besides, the Hope Fault is a strike-slip fault, whereas this event was a thrust fault! We at Ru wouldn’t be surprised if this event was slip (or slips, plural) on a combination of faults. In any case, there will much to learn from this event in the coming time. A discussion about the complexity of the tectonics in this area has already been posted on the USGS website.
Meanwhile, you can expect hundreds of aftershocks to fill your station helicorder screens in the coming days and weeks. If you get this message on Monday November 14th (local New Zealand time), you can see much of the action on our network page, similar to the image at the top of this post from Birkenhead Primary School.
Last week we welcomed James Hargest College, Invercargill and Koraunui School, Lower Hutt to the Ru Network. James visited the schools to help with set-up and run some Earthquake location demos with students. We were met in Invercargill by a reporter for an article in the Southland Times.
Thanks to all the students and teachers at both schools. We hope you enjoy using the seismometer to explore the Earth!
The Ru workshop took place on the 27th-29th January 2016. It was great to bring a group of people together with such passion and enthusiasm for teaching, to share ideas and contribute towards the seismometers in schools program.
Day 1 took place at the University of Auckland’s City Campus. The morning revolved around the Auckland Lablet; Physics experimentation on an Android tablet. There were demonstrations to showcase Lablet being used record and analyse several physics experiments and some very useful ideas came out of the discussion.
In the afternoon, the group were able to get their hands on the TC-1 Seismometer and built four from scratch. This showed just how simple it can be to construct the TC-1 and it was a great success when all four completed devices recorded data without a hitch.
There were several excellent talks over the rest of the afternoon. It was particularly interesting to hear (and see) how Jonathan had utilized an Arduino (a key component of the TC-1), to run a weather station.
Day 2 was spent on Waiheke Island. There were some great presentations by Dan Hikuroa, Caroline Little, Katrina Jacobs, Glenn Vallender, Michelle Salmon and Martin Smith. The day was nicely rounded off with some fantastic refreshments.
The highlight of Day 3 was undoubtedly the field trip to Rangitoto Island. The weather was excellent and although it was quite a hike up to the top, it was universally enjoyed. It was great to have Dan along as a guide to share his knowledge of the geology of the island and it was particularly interesting to explore the lava tubes.
Overall the workshop had a great turnout. We hope everyone enjoyed the three days and gained some ideas and insights that will be helpful in their schools.